Messier 33 (Triangulum Galaxy)

Better image here

Acquisition:

Bortle 7 skies
Nikon D5600 camera (unmodified)
ISO 200
Astro-Tech AT102ED refractor, 714mm focal length, f/7
HoTech 2" SCA field flattener (1X)
iOptron CEM26 mount
30s x 481 frames (4h 0.5m)

Processing:

Siril 1.2.1:

Crop to 4800 x 3600px
BQ Octantis' procedure of white balance, background subtraction, and histogram conditioning
StarNet++:
Background: modified asinh stretches (6x), background extraction, histogram adjustment, saturation
Stars: modified asinh stretch (5x), synthetic blue to reduce CA, saturation

RawTherapee 5.9:

L*a*b chrominance noise reduction
Luminance noise reduction

GIMP 2.10:

Luminance curve
Saturation
Black point